HDDs are common information storage devices. With improvements in recording density of magnetic HDDs, there has been a demand for improving the performance of magnetic heads and magnetic recording media. In a magnetic hard disk drive, a magnetic head is embedded in a slider that flies above the surface of a magnetic recording medium.
Recently, a technology so-called thermal assisted magnetic recording (TAMR) has been proposed, and a thermal assisted magnetic head also has been put to use. The technology uses a magnetic recording medium having high coercivity. When writing data, a write magnetic field and heat are applied almost simultaneously to the area of the magnetic recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization.
Commonly, the heat source comes from the thermal assisted magnetic head. FIG. 1A shows a perspective view of a conventional thermal assisted magnetic head 100. The thermal assisted magnetic head 100 includes a slider body 110 having an air bearing surface (ABS) (not shown, under) processed so as to provide an appropriate flying height and a light source unit 130 mounted on the slider body 110. The slider body 110 includes a bottom surface 112 opposite the ABS, a trailing edge 113 where read and write elements 115 are embedded, and a leading edge (not shown, back) opposite the trailing edge 113. The light source unit 130 is mounted on the bottom surface 112 and on the position where the write elements are embedded via a bonding layer. The light source unit 130 includes a laser diode 131 located near the write element and a mounting base 132 for supporting the laser diode 131. The mounting base 132 is bonded to the slider body 110 by using a solder layer, for example. The laser diode 131 emits a laser light to a portion of the magnetic recording medium, which reduces the medium's coercivity. After that, writing is performed by applying write magnetic field to the heated portion; therefore the writing operation is facilitated.
For ensuring the performances of the TAMR head, a serial testing for the TAMR heads must been carried out, including dynamic testing and static test. A conventional dynamic performance testing is performed at TAMR-level, namely the light source unit 130 has been bonded to the slider body 110 to form a TAMR head 100. In detail, firstly, the TAMR head 100 is mounted to a dynamic tester, and then, the laser diode 131 in the light source unit 130 emits a beam to an incident end of an optical waveguide 140 in the TAMR head, as shown in FIG. 1B, and then, the light power of the beam from the light source unit 130 will be detected to find the maximum light power position, and finally an optical alignment between maximum light power position and the incident end of the optical waveguide is made to start the dynamic performance testing.
Since the beam emitted by the laser diode is a Gaussian beam, the amplitude distribution of its cross section follows the Gaussian function, as shown in FIG. 1C, the amplitude of both sides is symmetrically reduced with the maximum amplitude intensity. Therefore, the optical waveguide must be precisely aligned to find the position of the maximum amplitude of the beam, that is, the maximum light power position. The dynamic performance testing is carried out after the accurate alignment, so as to find a defective head which will be discarded. This dynamic testing method at the TAMR level requires precise alignment of the beam, thus the testing efficiency is low, further the defective head screened out will be discarded, which makes the bonding process between the light source unit and the slider body meaningless, thereby wasting resources and increasing manufacturing cost.
Thus, it is desired to provide an improved method and system of testing dynamic performances for a slider body of a thermally-assisted magnetic head, before a light source unit is attached thereon, so as to screen out a defective slider to save the material cost and labor cost in the subsequent process.